Refrigeration systems are widely used in commercial and domestic applications for a wide variety of purposes. Some of the most well known domestic applications of refrigeration systems include home air conditioners, refrigerators, food freezers, and automotive air conditioners. In commercial applications, refrigeration systems are commonly used for cooling various systems during manufacturing processes, for example, large walk-in coolers and the cooling of machinery that generates heat during the manufacturing process. The operation of these refrigeration systems is well known, and generally, refrigerants such as R-12; R-22, R-500 and R-502, are used as the cooling medium for the refrigeration process.
On occasion these refrigeration systems may require servicing due to the rigorous operating conditions the systems are subjected to. Most refrigeration systems, if not properly maintained, will become overly contaminated with acids, moisture, air, and/or liquid sludge. These contaminants are extremely harmful to the primary components of the refrigeration system, and, especially, the compressor may have its life drastically shortened. Also, when a refrigeration system operates with contaminated refrigerant, the efficiency of the system is jeopardized and, therefore, the cooling capacity of the system is less than optimal.
In the past, service technicians have not paid close attention to the release of refrigerants, for example, chloralfluorocarbons (CFC) and hydrochloralfluorocarbons (HCFC), into the atmosphere when servicing refrigeration systems. However, in 1992 the United States Congress mandated new provisions under the Federal Clean Air Act which made it illegal for anyone to vent CFCs and HCFCs into the atmosphere. Furthermore, new EPA Regulations require heating, ventilation and air conditioning technicians to begin to recover refrigerants when servicing refrigeration systems. Also, further EPA regulations require a minimum vacuum of ten inches of Mercury to be obtained in the field unit being recovered to assure that the field unit is sufficiently evacuated. There are at least two types of refrigerant recovery systems that have been used by service technicians when they are servicing a refrigeration system. In general, these systems are expensive because of their complicated design, they employ a multitude of components, they are inefficient in their recovery of refrigerants, they are limited as to the type of gases they can recover, they have an inherent tendency to contaminate the recovery compressor and therefore shorten the life of the compressor, and are not well suited for usage in the field by a service technician because of their size limitations.
The first type of refrigerant recovery system generally employed to recover refrigerant from a refrigeration system uses a positive displacement compressor that is vulnerable to damage because it directly pumps contaminated refrigerant, air, moisture and/or liquid sludge through the compressor to a storage device, nearly all, if not all, of the time during the refrigerant recovery process. Because these compressors continuously place the principal fluid in direct communication with the compressor's oil sump, valves, cylinders, etc., oil level and oil quality become difficult to maintain. As a result, the compressor may become corroded from the acids, air, moisture and other contaminants within the system. This obviously may lead to a shortened compressor life, for example, less than a year, and, also, adversely affect the performance of the refrigerant recovery system.
The second type of refrigerant recovery system utilizes a closed refrigeration system such as that described in U.S. Pat. No. 4,539,817. In this type of refrigerant recovery system, a closed refrigeration system is provided separate from the field unit being serviced. The field unit could be, for example, a walk in freezer that could be used in a restaurant or an air conditioner unit that could be found in a residential home. The closed refrigeration system includes a condenser, compressor, a series of filters and valves, and a storage container having heat exchange coils located therein. The heat exchange coils located within the container are cooled to create a low pressure atmosphere within the container which is directly connected to the fluid refrigeration system to be serviced. This pressure differential between the field unit and the storage container allows refrigerant to be naturally drawn into the container. The container is capable of being disconnected from the closed refrigeration system through the use of a series of couplings. A new container can be hooked up to the closed refrigeration system and the cycle can be repeated. Because the closed refrigerant recovery system utilizes a storage container that employs evaporator coils located therein, the cost of each container becomes very expensive. Also, the coils increase the weight of the container and therefore decrease its mobility. Furthermore, because this system operates solely on the premise of a pressure differential created by the cooling effect of the heat exchange coils, the volume of recovered refrigerant is less than optimal because the system is incapable of reaching sufficiently low pressures within the container. The result is that a measurable quantity of refrigerant is stranded in the field unit when it is serviced. This quantity of refrigerant is sometimes dispersed into the atmosphere when the unit is being serviced, and therefore, it is not recovered and thus not recycled. And finally, because the container uses a series of couplings for interconnecting the storage containers, the opportunity for releasing refrigerant into the atmosphere is increased.
In light of the above-mentioned problems, it would be desirable to have a refrigerant recovery system that is portable, utilizes a refrigeration design that minimizes the components that are subjected to contaminated refrigerant, air and moisture, while being capable of removing 100% or nearly 100% of the refrigerant from the field unit being serviced. Such a system should minimize, if not entirely eliminate, the quantity of refrigerant dispersed into the atmosphere for environmental concerns and so that the maximum amount of refrigerant can be recycled. Also, such systems should be capable of creating sufficiently low vacuum pressures in the field unit in order to enhance the fluid recovery rate and recoverable fluid volume. Furthermore, it would be desirable if the recovery system could be universal so that various fluids could be recovered by a single recovery system. It would also be desirable to provide a refrigerant recovery system that is inexpensive, portable and lightweight in order to accommodate the needs of the field service technician.